The invention relates to fiber optic coupling devices suitable for use in fiber optic communication systems. It is of particular interest in optical fiber distribution networks, such as video communication networks.
Numerous methods are already known for coupling an output to a plurality of optical fiber inputs (the term "input" and "output" being used here solely for the sake of convenience and in no wise implying a particular direction of propagation of light). Coupling may be achieved by twisting fibers, then by drawing them so as to cause fusion thereof. Integrated optics have also been used, made from glass or from transparent plastic material, as well as coupling mixer "bars" and optical beams. Such approaches are difficult to carry out on an industrial scale or are unsatisfactory as regards the transmission characteristics the losses being excessive or distribution balance being difficult to obtain.
There is disclosed in U.S. Pat. No. 4,511,207 (Newton et al) a fiber optic data distributor having arrays of fiber lengths maintained in mutual alignment for light coupling by chips formed with V grooves. The lengths in one array may consist of successive loops of a same fiber. However, such a system as such does not constitute a m-to-1 coupler (m being greater than 1).
European specification No. 121 460 describes a blank suitable for making a "2-to-1" optical coupling device, comprising a convex fiber receiving groove formed in a first face of the piece. From such a blank, which has a single groove, a coupling device is formed by cutting it into two halves which are then placed opposite each other. The assembly of the two halves has a front face which may be joined to a centering unit receiving a connector end piece. Thus, a two branch coupler is formed which is of low cost and in which the two inputs may be balanced.